package 综合练习;

public class 爬楼梯 {
    public static void main(String[] args) {
        System.out.println(getSum(20));
    }
    public static int getSum(int number){
        if(number==1){
            return 1;
        }
        if (number==2){
            return 2;
        }
        if (number==3){
            return 4;
        }
        return getSum(number-1)+getSum(number-2)+getSum(number-3);
    }
}
